BACKGROUND: Cardiac arrest is a major public health issue affecting an estimated 300,000 patients in the United States each year. The American Heart Association has recommended the Simplified Acute Physiology Score II and III (SAPS) to assess severity of illness and to predict outcomes in the post-cardiac arrest population. Our objective was to determine if SAPS II and SAPS III scores predict outcomes in post-cardiac arrest patients.METHODS: We performed an observational study of patients suffering cardiac arrest with return of spontaneous circulation. Data were collected prospectively and recorded in the Utstein style. SAPS II and SAPS III scores were calculated for each subject. Logistic regression was used to assess the relationship between the calculated severity of illness score and in-hospital mortality and poor neurologic outcome.RESULTS: A total of 274 subjects were identified for analysis. SAPS II was a significant predictor of in-hospital mortality (OR: 1.05, 95% CI: 1.03-1.07) and poor-neurologic outcome (OR: 1.06, 95%CI: 1.04-1.08). SAPS III was a significant predictor of in-hospital mortality (OR: 1.04, 95%CI: 1.02-1.06) and poor neurologic outcome (OR: 1.04, 95%CI: 1.02-1.05). Both scores had moderate ability to discriminate survivors from non-survivors (SAPS II AUC: 0.70; SAPS III AUC: 0.66), and good neurologic outcome from poor neurologic outcome (SAPS II AUC: 0.71; SAPS III AUC: 0.65).CONCLUSION: SAPS II and SAPS III scores have only moderate discrimination and are not clinically relevant tools to predict outcome in post-cardiac arrest patients. Further study is needed to identify a more reliable severity of illness score in the post-arrest population.